1. Field of the Invention
The present invention relates to a point chisel for use with a power tool, in particular, a percussion power tool for working, in particular, stone and concrete.
2. Description of the Prior Art
Point chisels of the type described above have an elongate stem the power tool side of which is formed as a shank which is received in a chuck of a percussion tool with a possibility of a limited axial displacement, and a useful region extending to its workpiece pointed end that ends with a shaving or chipping active tip. As a result of its use, the tip wears off resulting in shortening of the workpiece side pointed section of the useful region. This leads to the increase of the chipping, active cross-section of the chisel, and the chisel becomes dull. However, stem cross-sections in form of a concave polygon are characterized by self-sharpening which improves the chipping capacity.
European Publication EP-0156789 A1 discloses a point chisel which is driven by a percussion power tool and has an elongate stem provided, at its power tool side, with a shank and having an outer diameter convexly tapering toward its workpiece end, a cross-section formed as a concave polygon with two or four axial grooves, and with the useful region having a prismatic core.
German Publication DE-19914522 A1 discloses a point chisel the useful region of which has a prismatic core and the cross-section of which is formed as a concave polygon with six grooves. The concave polygon extends only radially outwardly over the prismatic core, so that he self-sharpening effect takes place essentially when the useful region becomes dull in the intermediate and final sections of the useful region. In the initial section of the useful region, only the prismatic core is active, without self-sharpening of the chisel.
Accordingly, an object of the present invention is a point chisel having a particular high chipping capacity in the initial operational region of the useful region.